New Large-volume High P-T X-ray Diffraction Syste In Situ m at BL04B1 Earth’s interior is under extremely high pressure and high temperature conditions. Therefore, knowledge of the physical and chemical properties of Earth’s materials at high pressures and temperatures are indispensable for studying the structure, dynamics and evolution of Earth. In situ X- ray diffraction is a useful and powerful method for studying crystal structures, phase relations, e q uations of state, viscoelastic properties of minerals and melts at high P-T conditions. The KAWAI- type apparatus, together with a diamond anvil cell, is one of the most widely used high - pressure apparatuses, particularly in geosciences. The reason is that high pressures up to 30 GP a can be generated in relatively large volumes, rendering it possible to conduct sophisticated experiments with a complex sample assembly in fairly homogeneous high P- T conditions. I n SP ring -8 , a KAWAI- type apparatus for in situ X- ray observation, named SP EE D-1500 , was installed at the bending magnet beamline BL04B1 in 1997 [1] , and a number of important experimental results have been obtained. D espite the great success of SP EE D-1500 , further developments of high P- T in situ X- ray observation in a KAWAI- type apparatus are necessary to extend the pressure and temperature ranges. SP EE D-1500 was originally designed for experiments using tungsten carbide (WC) anvils, which limit the generated pressures to ca . 30 GP a. I n order to extend the pressure range, the use of sintered diamond (SD) is necessary. B ecause SD is very brittle, however, we need much more precise dimensions of the guide Fig. 2. Schematic drawing of the high-pressure vessel. The columns that support the upper and lower first- stage anvils (supporting columns) are separated from the main parts of the guide blocks so that the change in the relative dimension of the cubic compression space with press load can be minimized through adjustment. 100 mm Sliding block Supporting column First stage anvil Guide block Fig. 1. Photograph of the press part of SPEED-Mk II. block system and control of press load than those of SP EE D-1500 . A t high temperatures, grain growth of the sample materials is very rapid in a K awai - type apparatus. A s a result, we often miss many lines in diffraction patterns taken by SP EE D-1500 at high temperatures. I n such cases, we had very low precision in determining pressures and unit cell volumes of samples, and sometimes failed to identify the phases present. H ence, we need an oscillation system to obtain high -q uality diffraction patterns against grain growth. M ainly because of these two reasons, we have designed and installed the second KAWAI- type high P- T apparatus, SP EE D-M k II , at the same beamline BL04B1 (F ig. 1) [2] . The basic design of SP EE D-M k II has followed that of SP EE D-1500 . N amely, it is e q uipped with a DIA- type guide block system, a hydraulic system for maximum press load of 15 MN , a heating system, and a hori z ontal goniometer with a G e -SSD for energy - dispersive X- ray diffraction. S ix first - stage anvils on the DIA- type guide block system compress a cubic space for a KAWAI- type assembly composed of eight second - stage cubic anvils, each with a truncated corner. O ne of the serious problems for pressure generation in such a system is that the compression space deforms with 90 References [1] W. Utsumi et al. : H i gh Pre ss. Sc i. Technol . 7 ( 1 998) 1 484 . [ 2 ] T . Ka tsu ra, K . F u nako s h i , A . K u bo, N . N is h i ya m a, Y . Tange, Y . S u eda, T . K u bo and W. Utsumi : Phy s. Ear t h Plane t. In t. 143 - 144 (2004) 497 . To m oo Ka tsu ra a and Ken- i ch i F u nako s h i b (a) In stitut e for S tu dy of t he Ear t h’ s In t er i or, Okaya m a U n i ver sit y (b) SPr i ng-8 / JASRI E- m a i l: t ka tsu ra@ mis a s a . okaya m a- u. ac . jp Intensity (111) (200) (220) (311) (222) (400) (331) (420) (422) Pb K α 2 Pb K α 1 Pb K β 1,3 Pb K β 2 At 2070 K with oscillation 2 θ = 7.017 Energy (keV) 40 50 60 70 80 90 100 110 120 40 50 60 70 80 90 100 110 120 At 2070 K without oscillation 2 θ = 7.017 (111) (200) (220) (311) (222) (400) (331) (420) (422) Pb K α 2 Pb K α 1 Pb K β 1,3 Pb K β 2 Intensity Energy (keV) Fig. 3. Diffraction patterns of MgO with and without oscillation at 3 GPa and 2070 K: (a) diffraction pattern taken without oscillation, and (b) with oscillation. The MgO peaks are labeled by the lattice index. The peaks by Pb fluorescence are labeled as PbK α 1 and so on. i ncrea si ng pre ss load, wh i ch m ay ca us e blow- o ut or break i ng of SD anv i l s. In fac t , t he hor i zon t al d im en si on of t he co m pre ssi on s pace i ncrea s e s rela ti vely t o t he ver ti cal one w it h i ncrea si ng pre ss load a t a ra t e of 1 3 μ m /MN i n SPEED- 1 500 . In order t o f i x t h is proble m , t he col um n s su ppor ti ng t he t op and bo tt o m f i r st - st age anv i l s are s epara t ed fro m t he m a i n par t of t he g ui de block s s o t ha t t he st reng t h su ppor ti ng t he s e anv i l s can be adj ust ed wh i le exa mi n i ng t he rela ti ve defor m a ti on of t he co m pre ssi on s pace (F i g . 2) . By repea ti ng adj ustm en ts , t he ra t e of t he rela ti ve defor m a ti on ha s been su ppre ss ed t o 4 μ m /MN . In add iti on t o t he d im en si on s of t he co m pre ssi on s pace, t he pre ss load is al s o con t rolled prec is ely i n SPEED-Mk II . The pre ss load is con t rolled w it h d i v isi on s of 20 ~ 30 kN i n SPEED- 1 500, wherea s it is con t rolled w it h 3 kN d i v isi on s i n SPEED-Mk II . F u r t her m ore, t he hydra u l i c s y st e m is eq ui pped w it h t wo i nver t er p um p s , wh i ch ro t a t e i n propor ti on t o t he d i fference be t ween t he s e t and real load s s o a s t o allow sm oo t h co m pre ssi on and deco m pre ssi on . Beca us e of t he s e im prove m en ts , we have su cceeded i n ex t end i ng t he pre ssu re range genera t ed by a Kawa i - t ype appara tus. The h i ghe st pre ssu re genera t ed by SPEED- 1 500 is 40 GPa, wherea s pre ssu re of 63 GPa ha s been ach i eved by SPEED-Mk II ( i n Feb . 2004, by E . I t o, ISEI, Okaya m a U n i ver sit y) . SPEED-Mk II is placed on a st age s y st e m m a i nly for po siti on i ng t he s a m ple s t o t he d i ffrac ti on area . The st age s y st e m ha s one ro t a ti on ax is aro u nd t he ver ti cal d i rec ti on ( κ -ax is ) fro m – 7 t o 1 3 . Th is κ -ax is is us ed for con t roll i ng t he s a m ple o s c i lla ti on . F i g u re 3 s how s d i ffrac ti on pa tt ern s of MgO a t 3 GPa and 2070 K collec t ed w it h and w it ho ut opera ti ng t he o s c i lla ti on s y st e m. Many of t he MgO peak s are no t ob s erved i n t he d i ffrac ti on pa tt ern t aken w it ho ut o s c i lla ti on (F i g . 3(a)) . On t he con t rary, m o st of t he m are ob s erved i f t he o s c i lla ti on is opera t ed (F i g . 3(b)) . The pre ss st age co u ld be ben t d u r i ng o s c i lla ti on beca us e t he pre ss is very heavy (20 t on) . Spec i al a tt en ti on wa s pa i d t o de si gn i ng t he st age su ch t ha t s h i f ts of t he s a m ple w it h o s c i lla ti on can be su ppre ss ed t o 50 μ m. Th us , we have im proved a Kawa i - t ype appara tus for in situ X-ray d i ffrac ti on t o ob t a i n h i gh-q u al it y d i ffrac ti on pa tt ern s a t h i gher t e m pera tu re s and pre ssu re s. W e expec t t ha t a n um ber of im por t an t exper im en t al re su l ts w i ll be ob t a i ned usi ng t h is appara tus. 91
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